This invention relates to electrical resistance heaters and coil insulators therefor, and more particularly, to a coil insulator for mounting adjacent convolutions of an electrical resistance heating coil, the insulator employing point suspension to mount the convolutions. The insulator has the advantages of eliminating coil bowing, and the insulator can be used in an automated assembly process for manufacturing a resistance heating assembly. Insulators for mounting convolutions for both one and two reaches of coil are described.
In heating units for use in a variety of appliances, electrical resistance heating elements are mounted on a frame and convolutions of an electrical heating coil are carried on the insulator to electrically isolate the heating element from the frame. There are a variety of insulators which have been designed for this purpose; among these being insulators such as shown and described in U.S. Pat. Nos. 4,692,599, 4,675,511, 4,559,412, 4,531,017, 4,472,624, 4,458,141, 4,363,959, 4,268,742, 4,268,189, D262,285, and D261,260. All of these insulators are designed to support a plurality of coil convolutions with some of the insulators supporting two adjacent convolutions, and some of the insulators supporting three.
Previous insulator designs have a variety of drawbacks. Some allow coil convolutions to be supported only on one side of the insulator. Others are not readily susceptible for use in automated assembly processes. Hand insertion of insulators and installation of coil convolutions onto the installed insulator is both time consuming and costly. This latter is particularly true of three point suspension insulators such as taught in the '511, '189, and '017 patents referred to above. Another problem with three point suspension insulators is that bowing of the coil can occur between insulators. This can lead to shorting of the coil. Other problems with previous insulators is their lack of ability to retain coil convolutions in place when vibrations are experienced in an appliance. Severe vibrations, or vibrations occurring over prolonged periods of time can dislodge a convolution from its associated insulator. The unrestrained convolution is now free to contact either the frame for the heating unit, or another convolution. In either instance, an electrical short results, According to the present invention, a new electrical insulator is provided which prevents dislodging of coil convolutions because of vibrations, or handling of the unit during storage, transport, or installation.